The goal of this project is to purify and determine the structure of two proline transfer RNAs which misread the genetic code. In the early 1970s several different classes of frameshift suppressor mutations were isolated in Salmonella typhimurium. Evidence was presented that in three of these classes genetically altered proline tRNAs were responsible for misreading the genetic code and subsequent frameshift suppression. We plan to characterize these proline tRNAs and determine how they cause translational suppression of frameshift mutations. The experimental procedure will be the purification of the tRNAs in question by a combination of the "solid-phase" technique of Goss and Parkhurst and RPC-5 column chromatography. The tRNAs will be sequenced using both the terminal-labeling technique and the Sanger fingerprinting methods. Comparison of the sequence of tRNAs from the wild type and from the suppressor strains will probably reveal differences in the anticodon region, differences that allow the suppressor tRNA to translate a four-base codon.